You can make this more workable if what you have configured inside Cubase matches what is really occurring in your hardware. You don’t really have a reverb, compressor, or other effect connected to your audio interface. What is really sitting on the I/O of you audio interface is a patchbay (or perhaps just some jacks ). That is what you want to create a device for that can be used as an fx insert in the MixConsole. That is the device you want to have input & output channels permanently assigned to. And it is gonna be a dumb device 'cause it really doesn’t do much.
However, say you have created (or plan to create) a MIDI Device that has all the patches for your reverb and maybe even a really nice device panel with knobs you can change settings on the reverb. You don’t want to loose that capability and you don’t need to. Take that midi device and create a 2nd External FX (or Instrument see below*) except don’t assign anything to its audio In or Out (so now it is not hogging any audio I/O) this device can now be used to control your reverb via midi while the audio will go through your patchbay device. Repeat as needed for your other FX gear.
*For these devices used to control the hardware it probably works better to create them as External Instruments rather than External FX because you can then easily see the outboard equipment’s presets.
Granted this is an extra hoop to jump through but the intention of External FX and Instruments is to create a single entity that integrates the MIDI control of a device with its audio I/O. By swapping out gear you are basically making that integration impossible (not really, but that’s another post) and to resolve this situation you need to separate the audio and midi control elements of your external FX and control them independently in Cubase.